Thank you, can you find a reference for Sarahs birth certificate - if I ordered that then that may confirm the details.
Looking at the 1851 census, I agree with you about 2 Sarah Riddles, but 'my' Sarah was living with her mother Elizabeth and brothers and sisters. What is interesting about that census is that it states Elizabeth as the head of the household and as unmarried.
The 1841 census, has her living with James Riddle.
Ordering her birth certificate would confirm things further.